The veterinary studies area conducts epidemiologic investigations using data compiled by North American veterinary university teaching facilities, the Armed Forces Institute of Pathology, NCI's Experimental Tumor Registry, and other sources when available. These investigations evaluate the role that environmental factors have in the etiology of cancer in animals, particularly to identify situations where the companion domestic animal may serve as a sentinel for human exposures to environmental carcinogens. Major areas of current interest are the necropsy findings among military working dogs who served in Vietnam during 1968-1973, household and lawn chemical exposures of pet dogs diagnosed with malignant lymphoma, and similar chemical exposures of pet dogs diagnosed with cancer of the lower urinary tract. A case-control study comparing the neoplasm experience at necropsy of 1,200 Vietnam service military working dogs compared with those that served in the U.S. found that Vietnam service dogs had a significant 2.0-fold excess of testicular seminoma. A case-control study of 491 pet dogs with malignant lymphoma found a significant 1.3-fold association with owner use of phenoxy herbicides plus a professional lawn care service. A case-control study of 85 pet dogs with cancer of the lower urinary tract found significant associations with owner use of lawn insecticides and professional lawn care service companies, and professional grooming service plus exposure to flea and tick dips.